In the prior art, there is the wiring substrate on which an electronic component such as a semiconductor chip, or the like is mounted. In an example of such wiring substrate, the build-up wiring is formed on one surface or both surfaces of the core substrate by the semi-additive process, or the like.
In recent years, with the enhancement in performances of an electronic component such as a semiconductor chip, or the like, a narrower pitch of the wiring layers in the wiring substrate is being advanced.
A related art is disclosed in Japanese Laid-open Patent Publication No. 2002-252459.
As explained in the column of the preliminary matter described later, in the case that the multilayer wiring is formed by using the semi-additive process, when the desmear process is applied to the inside of the via holes, a surface of the insulating resin layer is also etched and roughened simultaneously. Accordingly, the wiring layers can be formed on the insulating resin layer with good adhesion by the anchor effect.
In recent years, with the progress of size reduction and higher performance of the semiconductor chip, the further miniaturization of the wiring layers of the wiring substrate is requested.
In such a situation that unevenness is produced on a surface of the insulating resin layer, particularly when a narrower pitch of the wiring layers is advanced, the residue is ready to occur upon etching the seed layer. Therefore, an electric short-circuit is easily caused between the wiring layers. Further, such a problem exists that a transmission loss of the high-frequency signal is ready to occur, in the wiring layers which are formed on the unevenness of the insulating resin layer.
In this manner, in the method of ensuring adhesion of the wiring layers by roughening the surface of the insulating resin layer, particularly, it is difficult to form the fine wiring layers whose line width is 10 μm or less with good reliability. As a result, the technology to form the fine wiring layers on a smooth resin layer with good adhesion is demanded.